One of the issues I’ve been struggling with in building MCsla is that the mgx tool that is used to compile a DSL into M doesn’t output valid M in all cases.

A couple of the issues are simply unsolvable (I mentioned these in my last blog post as well).

If your grammar includes any Boolean values, they come out as ‘ true’ and ‘false’ (including the single quotes), when they should come out as true and false (no quotes).

If your grammar includes any lists of values, a single-item list generates invalid M, while multi-item lists generate valid M (though I’m not sure you can describe the result using an MSchema – but at least the result is “valid”).

As I say, these problems are “unsolvable” because the M rendering API is what creates the bad result, and that’s a black box.

The solution, such as it is, requires taking the text output, the M code, and doing some text processing to fix the issues. In the olden days I’d have whipped up an awk script to do this, but these days C# is the tool (even if it is a lot more verbose). Here’s the code I’m using to fix the two issues – kind of a post-processor to the mgx tool:

Working with Microsoft Oslo, the goal is to enable the creation of a domain specific language (DSL) using MGrammar, so a developer can write code in that grammar, compile the code into M and then load that M into the Oslo repository.

This is turning out to be a bigger challenge that you’d expect, though I think that’s largely because I’m dealing with such early builds of all the Oslo tools.

The tool chain for compiling DSL source into M is this:

Use mg.exe to compile the MGrammar

Use mgx.exe to compile the DSL source against the grammar to create M

Use m.exe to compile the M

Use mx.exe to load the compiled M (an mx file) into the repository

Unfortunately this breaks down at step 2, because mgx.exe has some issues.

The first issue I encountered was that mgx creates hierarchical M, not relational M. What’s the difference?

Relational M is defined by an MSchema where child entities define foreign key relationships to their parent. This is the normal model you’d find when creating any relational database.

Hierarchical M is defined by an MSchema where parent entities define relationships with their children. This is more like what you’d find in XML, and doesn’t completely map to a normal relational model. While it is true that this type of MSchema can result in valid SQL table definitions, you can’t define all the relationship restrictions you’d normally want to have in your database.

The thing is, M code itself must match the shape of the MSchema you want to use. So if you define your entities using a relational MSchema, the M must also be relational. Conversely, this means that when mgx generations hierarchical M, you must use a hierarchical MSchema to map that M metadata into your database (or the Oslo repository).

This is an unfortunate limitation, that hopefully will be resolved at some point.

The second and third issues I encountered appear to be bugs in mgx. But not just in mgx – they are bugs in the underlying API, so even if you try to write your own “mgx replacement” (which is what I’m doing btw), the API that helps you generate M will create invalid M output.

The two bugs are:

When a node has a Boolean value, true comes out as ‘ true’ and false comes out as ‘ false’. The single quotes and space after the first single quote should not be there, but that’s what gets output. Oddly enough, Int32 and other primitive types work fine – just Boolean types seem to be broken.

When a list of items is output, and that list contains one item, the output is invalid M. Multiple items or no items in the list work fine – just the single-item case is broken.

The only solution I’ve found for these bugs is to do a post-processing step on the resulting M – literally doing text processing to identify and fix the issues. Again, hopefully these issues get resolved in the API itself, so valid M gets produced by mgx or any other tool using the API.

The fourth issue, and the reason I’m writing my own mgx replacement, is that my MCsla grammar allows arbitrary placement of various elements, like authorization and business rules within a property:

Because the grammar allows arbitrary placement, the resulting M is a collection of mixed types of entity. In other words, the compiled M is effectively invalid, because the M parser can’t figure out whether the collection contains auth rules, or business rules (because it contains both).

I really have two choices – either change my grammar to put auth rules and business rules in different block structures, or at least to require one to come before the other. Or write my own mgx replacement to rearrange the nodes of the compiled DSL code into discrete collections of homogeneous types.

Since I don’t want to “ruin” my pretty grammar, I’m trying to fix the nodes by creating my own mgx replacement. And this seems quite realistic, though it doesn’t address the first three issues in any way – those are still problematic.

I have the first three segments of the CSLA .NET for Silverlight video series available now, and so I'm extending a special pre-purchase offer to anyone who wants to get access to the content as it becomes available.

Buy now and save $100 off the regular purchase price. This special offer gives you immediate access to the first three video segments, and will give you access to the remaining video segments as they become available. You can be among the first to have access to this great content!

Introduction In this video you will become familiar with the CSLA .NET framework's vision, goals and overall scope. You will be introduced to the various architectures supported by CSLA .NET for Silverlight, and the requirements necessary to build Silverlight and CSLA .NET for Silverlight applications.

The Basics This video details the basic steps of creating a CSLA .NET business object that interacts with a server-side web service to get its data. The process of using data binding to connect the object to the Silverlight UI is also covered. At the end of this video you will understand all the basic steps and coding structures necessary to build a simple CSLA .NET for Silverlight application.

Client-only Architectures This video covers the various client-only scenarios supported by CSLA .NET for Silverlight, including true client-only applications and “edge” applications that interact with remote services. This video builds on The Basics to dive deeper into the various options for building client-only applications.

N-tier Architectures - coming soon In this video you will learn how to build 2-, 3- and 4-tier applications using CSLA .NET for Silverlight. CSLA .NET allows your UI, business object and data access code to remain the same in all these configurations, but there are numerous configuration options and choices you can make to optimize how your application works in each of these scenarios.

Business Object Types - coming soon In this video you will learn how to implement each of the business object stereotypes supported by CSLA .NET. These include editable objects, lists of objects, read-only objects, read-only lists, name/value lists, command objects and more. At the end of this video you will understand the purpose behind each stereotype, and the coding structure to use when building business objects for each stereotype.

N-tier Data Access - coming soon This video details the various options supported by CSLA .NET for data access in n-tier scenarios. You will learn how to put data access code into your business class, or into a separate data access assembly, along with the pros and cons of each technique. You will also learn about the ObjectFactory attribute and base class, that can be used to create pluggable data access layers for an application.

Authentication and Authorization - coming soon In this video you will learn about the various authentication and authorization techniques supported by CSLA .NET for Silverlight. Authentication options include Windows, ASP.NET Membership Provider and custom authentication. Authorization is the same as CSLA .NET for Windows, and includes per-property and per-type authorization, along with Silverlight UI controls to simplify the creation of your interface

The really cool part? This is at a theater and everyone will get to see the new Star Trek movie after the technical content.

How cool is this??? See some cool Silverlight and other tech content, and then watch a private screening of the new movie?

And I know that a lot of local Microsoft experts will be attending as well – you know, the people that live in the area and organize our user groups, write books and do a lot of speaking. So this is also an opportunity to hang out with “people in the know” :)

See you there! Live long and prosper!

(though I still wonder if I’ll get past seeing Syler every time Spock is on screen…)

I’m working on a number of things at the moment. Most notably the CSLA .NET for Silverlight video series that will be available in the very near future (it turns out that creating a video series is a lot of work!). And of course I’m prepping for numerous upcoming speaking engagements, and I’d love to see you at them – please come up and say hi if you get a chance.

But I’m also working on some content around Microsoft Oslo, MGrammar and related concepts. To do this, I’m creating a prototype “MCsla” language (DSL) that allows the creation of CSLA .NET business objects (and more) with very concise syntax. I’ll probably be blogging about this a bit over the next couple weeks, but the goal is to end up with some in-depth content that really walks through everything in detail.

My goal is for the prototype to handle CSLA editable root objects, but covers business rules, validation rules and per-type and per-property authorization rules. Here’s a conceptual example:

But what I’ve realized as I’ve gotten further into this, is that I made a tactical error.

A lot of people, including myself, have been viewing MGrammar as a way to create a DSL that is really a front-end to a code generator. My friend Justin Chase has done a lot of very cool work in this space, and he’s not alone.

But it turns out that if you want to really leverage Microsoft Oslo and not just MGrammar, then this is not about creating a code generator. And what I’m finding is that starting with the DSL is a terrible mistake!

In fact, the idea behind MOslo is that the DSL is just a way to get metadata into the Oslo repository. And you can use other techniques to get metadata into the repository as well, including the graphical “Quadrant” tool.

But my next question, and I’m guessing yours too, is that if all we do is put metadata into the repository, what good is that???

This is where a runtime comes into play. A runtime is a program that reads the metadata from the repository and basically executes the metadata.

I always had a mental picture of MOslo “projecting” the metadata into the runtime. But that’s not accurate. It is the runtime that “pulls” metadata from the repository and then uses it.

And that’s OK. The point is that the runtime is this application that interprets/compiles/uses/consumes the metadata to end up with something that actually does some work.

What I’m learning through this process, is that the DSL exists to service the metadata in the repository. But it is the runtime that defines the metadata. The runtime consumes the metadata, so the metadata exists to serve the needs of the runtime.

In other words, I should have started with the runtime first so I knew what metadata was required, so I could design a DSL that was capable of expressing and capturing that metadata.

The example MCsla code you see above is OK, but it turns out that it is missing some important bits of information that my runtime needs to function. So while the DSL expresses the important CSLA .NET concepts, it doesn’t express everything necessary to generate a useful runtime result…

So at the moment I’ve stopped working on the DSL, and am focusing on creating a working runtime. One that can execute the metadata in a way that the user gets a dynamically created UI (in WPF) that is bound to a dynamically created CSLA .NET business object, that leverages a dynamically created data access layer (using the CSLA .NET 3.6 ObjectFactory concept). I’m not dynamically creating the database, because I think that’s unrealistic in any real-world scenario. We all have pre-existing databases after all.

Once I get the runtime working (and it is close – here’s a screenshot of a simple object, showing how the dynamic WPF UI is running against an object with business rules, buttons bound to the CslaDataProvider through commanding and all the other nice CSLA features.

Not that my UI is a work of art, but still :)

I have a lot more to do, but it is now clear that starting with the runtime makes a lot more sense than starting with the DSL.

VS Live Las Vegas is coming up soon, and as a speaker I am able to provide a special discount code – kind of a perk for you reading my blog I guess :)

If you register for VS Live using code S9V03 you’ll get the all-access passport package for $400 off the standard price.

The conference has great content for developers, covering core .NET, VSTS/TFS, Silverlight, WPF, ASP.NET, Azure, Oslo and more. VS Live is one of the most respected independent technical conferences in the Microsoft space.

I’ll be talking about parallel and concurrent programming (from a practical, real-world perspective), techniques you can use to deal with the rapid pace of change in technology, and giving a workshop on building distributed applications using .NET 3.5 SP1 (so WPF, Silverlight, WCF, Windows Workflow – and of course a liberal dose of CSLA .NET).

As a nice bonus, the conference has a block of rooms at the Venetian Hotel for $99/night. This is one of the nicest hotels in Vegas, and normally you couldn’t touch a room for anywhere near this rate!

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Planning for Successful Outsourcing

April 30, 11:00 PT, 1:00 CT, 2:00 ET Outsourcing is a popular strategy for decreasing the cost of supporting and maintaining business applications. Done right, it can be a successful strategy. Join Magenic as we discuss and dissect why outsourcing has gained the attention and approval of business and IT managers and how to navigate a pain-free transition. read more ...